Hyperbolic navigation systems such as loran and omega, as well as satellite navigation systems have been utilized to place the position of a vessel within plus or minus fifty feet in certain circumstances. While these units have operated separately quite satisfactorily to give the operator of a vessel an idea of his location, unless expert personnel are utilized in the operation of this equipment, due to its complexity it is almost impossible in an emergency situation to instruct a person on how to utilize the particular navigation unit.
In order to overcome the complexities of indicating position under emergency situations in which panic is likely to occur, the Coast Guard has in the past reviewed a system in which a transponder tethered to a vessel is utilized to receive the hyperbolic navigation signals and to retransmit them to Coast Guard reception points where they are processed so that the location of the vessel can be ascertained. Typically these devices are of a low power variety and are carried by a helium filled balloon or other such device as high above the vessel as possible while still being tethered thereto in order to provide for increased range and reliability necessary in order to locate the vessel. Unfortunately, either due to cost or due to problems with such low level retransmitted signals, such a system is not presently in place and it is only with difficulty that the Coast Guard or other agency can locate a vessel in distress.
While it has long been possible to locate vessels in distress through the utilization of emergency locators beacons and triangulation, success with triangulation in terms of the personnel utilized for such purposes, as well as the variability of the equipment involved, make such triangulation systems unreliable. A further reason for the unreliability in such systems is the variable signal strength of the transmitters utilized on the vessels in distress.
While it is indeed true, that individuals can turn on their loran or other navigation units and read the latitude and longitude directly into a microphone coupled to a transmitter such as a VHF transmitter, under panic situations this is not always possible. Moreover due to the complexity of the front panels of most hyperbolic or satellite navigation units an uninitiated person cannot adequately even turn on the unit much less obtain the required reading to be able to transmit it by radio.
It is therefore an object of this invention to provide a more foolproof method of providing the location of a vessel in distress to the appropriate authorities in an automatic fashion which can be simply utilized and which utilizes existing emergency frequencies.
It is also an object of this invention to provide a system which is disabled by the appropriate authority through the utilization of a specialized channel once the information as to location has been ascertained or once the vessel has been physically sighted.
A further object of the present invention is to provide that the transmission of emergency information does not impair the operation of the navigation receiver either through interference or inadvertent overload.